Preform holding jig for biaxial orientation blow molding

ABSTRACT

A holding jig for such a preform formed of a synthetic resin into a bottomed cylindrical shape as is to be assembled by inserting a mouth cylinder portion to an insertion limit into the leading end portion of a cylindrical jig body having a pin inserting bore formed therethrough at its center for a drawing pin to be inserted thereinto. The holding jig comprises a support portion disposed in the inner circumference of the leading end portion of the jig body at a position to confront a peripheral projecting ridge of the mouth cylinder portion, for making such external contact with the outer circumference of the peripheral projecting ridge as to insert and extract of the mouth cylinder portion, thereby to hold the assembled posture of the preform. The holding jig can hold the preform stably in a predetermined posture thereby to achieve a high productivity for the biaxial orientation blow-molded bottle.

TECHNICAL FIELD

[0001] The present invention relates to a structure for a preformholding jig to be used in a method of biaxial orientation blow moldingof a bottle of a synthetic resin.

BACKGROUND ART

[0002] Biaxial orientation blow-molded bottle made of a synthetic resin,especially biaxial orientation blow-molded bottle of a polyethyleneterephthalate resin are used in many fields and in large numbers asbottle containers, because they exhibit a number of excellent features.

[0003] This biaxial orientation blow-molded bottle of a synthetic resinis generally manufactured by biaxially drawing in the axial directionand in the radial direction and blow-molding a preform, which has beeninjection-molded into a bottomed cylindrical shape, while heating it toa temperature capable of developing the orientation effect.

[0004] According to a method of the prior art, as described inJP-A-1995-290562 and shown in FIG. 14, a preform P, which is so held bya holding jig 5 as is loosely fitted in an inverted posture by a guidecylinder member 10 and which is heated to a temperature capable of thedrawing effect, is assembled with a blow mold 1 together with theholding jig 5 such that a neck ring P1 formed integrally with andcircumferentially of the lower end of the outer circumference of a mouthcylinder portion P2 of the preform P is retained on a neck supportingflanged portion. 3 of the blow mold 1. The preform P is axially drawnand molded in the axial direction by a drawing pin 16, which is insertedinto a pin inserting bore 11 formed through in the center of the holdingjig 5, and is drawn and molded in the radial direction with the blowair, which is pumped in through the pin inserting bore 11 or the drawingpin 16, so that a bottle P1 is molded.

[0005] In the method of the prior art described above, the posture ofthe preform is loosely retained mainly by the guide cylinder member 10.

[0006] In JP-A-1997-314650, for example, there is described a doubleblow molding method. This method includes: the step of biaxialorientation blow molding the preform into a primary intermediatemolding; the step of heating and thermally shrinking the primaryintermediate molding into a secondary intermediate molding; and thefinal step of blow molding the secondary intermediate molding into abottle. The bottle manufactured can have little residual strain and ahigh heat resistance.

[0007] In the method of the prior art, however, especially with theholding jig being detached from the blow mold, the preform is justloosely fitted at its mouth cylinder portion in the holding jig. Therearise problems that the posture is broken while the preform is beingtransferred, to cause production troubles., and that the posture of thesecondary intermediate molding being heated during the double blowmolding is deflected to cause defective phenomena such as the bite ofthe mold.

[0008] According to the method of the prior art in which the assembledposture of the preform is held by inserting the guide cylinder portioninto the mouth cylinder portion of the preform, moreover, that effectivesectional area of the inside of the mouth cylinder portion of thepreform, which can be utilized as a passage for the blow air, is reducedto raise a problem that it is impossible to achieve the improvement inproductivity, which has been intended by increasing the flow rate ofblow air to shorten the blow time period.

[0009] Just after the blow molding, moreover, there are found many stepsof cooling the bottle by an air circulation to blow air into the bottle.These steps are executed mainly through an air passage formed in thedrawing pin. However, there is a desire to enlarge the air passage, toincrease the air flow rate, to raise the cooling efficiency thereby toimprove the productivity better. The reduction in the effectivesectional area of the mouth cylinder portion also raises a problemagainst those demands.

[0010] Therefore, the present invention has been conceived to solve theaforementioned problems of the prior art, and has a technical object tohold a preform stably in an assembled posture thereby to achieve a safeand high productivity of the biaxial orientation blow-molded bottle.

[0011] Another technical object is to enlarge the passage of air intothe preform thereby to achieve a high productivity of the biaxialorientation blow-molded bottle.

DISCLOSURE OF THE INVENTION

[0012] In the present invention for solving the aforementioned technicalproblems, the means of the invention as set forth in claim 1 has thefollowung configuration.

[0013] the preform holding jig for biaxial orientation blow-moldingmounting a support portion holding an assembled posture of a preformhaving a bottomed cylindrical shape formed by a synthetic resin which isassembled by inserting a mouth cylinder portion until an insertionlimit, into the leading end portion of a cylindrical jig body in which apin inserting bore is formed in the center for inserting a drawing pintherein.

[0014] Wherein said support portion is disposed in the innercircumference of the leading end portion of said jig body at a positionopposed to a peripheral projecting ridge of said mouth cylinder portion,and for making external contact with the outer circumference of saidperipheral projecting ridge as to be capable of inserting and extractingsaid mouth cylinder portion.

[0015] According to the aforementioned construction of claim 1, thesupport portion disposed in the inner circumference of the holding jigmakes it possible to insert and extract the mouth cylinder portion sothat the insertion and extraction can be performed, if necessary, in themanufacturing process of the bottle. Here, the insertion limit of themouth cylinder portion can be set, for example, by the neck ring formedintegrally with and circumferentially of the lower end of the outercircumference of the mouth cylinder portion, by the upper end portion ofthe mouth cylinder portion and the leading end face of the jig body, orthe peripheral abutment against the circumferential step portionsuitably added.

[0016] Moreover, the support portion is constructed to hold theassembled posture of the preform with the holding jig while makingcontact with the outer circumference of the peripheral projecting ridgeof the preform. The preform can be held stably in a predeterminedassembled posture by the support portion, even when the molding jig isnot only attached to but also detached from the blow mold, and therocking motion of the preform can also be inhibited to prevent theoccurrence of production troubles, as might otherwise be caused bylosing the posture during the transfer. Therefore, the rocking of theposture of the secondary intermediate being heated in the double blowmolding can be eliminated to prevent the defective phenomenon such asthe bite of the mold.

[0017] Here, the peripheral projecting ridge is formed in acircumferential ridge shape on the outer circumference of the mouthcylinder portion and at a position below the helical ridge and is namedthe bead ring or the step portion, too, so that it is utilized as theretaining portion of a pilfer-proof cap.

[0018] In the double blow molding method, the secondary intermediatemolding shrunk from the primary intermediate one is mounted in a splitmold and is blow molded. This secondary intermediate molding is notalways fixed due to the thermal shrinkage but is slightly smaller inmost cases than the final molding. With a small deflection of the heldposture, the defective phenomena such as the contact with the split moldor the bite by the split mold is caused. Therefore, the aforementionedholding jig as set forth in claim 1 exhibits extremely effective actionsand effects in the double blow molding method.

[0019] On the other hand, this support portion holds the posture of thepreform from the outside of the preform thereby to inhibit the rockingmotion of the preform. This method makes it unnecessary to provide theposture holding portion in the mouth cylinder portion of the preform.

[0020] Therefore, the inside of the preform can be effectively utilizedin its entire inside for the flow passage of the blow air so that theblow air flow can be used to the maximum. This makes it possible toshorten the blowing time period and the cooling time period by the aircirculation after the blow thereby to improve the production efficiency.

[0021] In the invention of claim 1, the means of the invention as setforth in claim 2 assembles and fixes an O-ring in an inner circumferencegroove formed in the inner circumference of the leading end portion ofthe jig body thereby to construct the support portion.

[0022] According to the aforementioned construction as set forth inclaim 2, the mouth cylinder portion can be easily inserted and extractedwhile sliding with the O-ring. Moreover, the O-ring supports makesexternal contact with the entire outer circumference of the peripheralprojecting ridge so that the assembled posture of the preform can beheld properly and stably and so that the structure of the supportportion is simplified.

[0023] In the invention of claim 1, the means of the invention as setforth in claim 3 assembles and fixes holder spring in an innercircumference groove formed in the inner circumference of the leadingend portion of the jig body, thereby to construct the support portion.

[0024] According to the aforementioned construction as set forth inclaim 3, the mouth cylinder portion can be easily inserted and extractedby utilizing the function of the holder spring, and the holder springmakes external contact with the outer circumference of the peripheralprojecting ridge so that the posture of the preform can be held properlyand stably by the elastic force of the holder spring, as set to adesired value.

[0025] In the invention as set forth in claim 3, the means of theinvention as set forth in claim 4 is constructed by using the holderspring, which makes external contact with the outer circumference of theperipheral projecting ridge of the preform at a plurality of pointspositioned at substantially equally spaced central angles.

[0026] According to the aforementioned construction as set forth inclaim 4, the mouth cylinder portion is supported at a plurality ofpoints positioned at the substantially equally spaced central angles,without making external contact with the entire outer circumference ofthe peripheral projecting ridge. Therefore, the attachment anddetachment of the preform can be achieved smoothly and reliably with alow resistance to the insertion and extraction.

[0027] In the invention as set forth in claim 4, the means of theinvention as set forth in claim 5 is constructed by using the holderspring makes external contact with the outer circumference of theperipheral projecting ridge of the preform at three points positioned atsubstantially equally spaced central angles.

[0028] According to the construction as set forth in claim 5, a two- orfour-point support of the mouth cylinder portion is unstable, but themouth cylinder portion is supported at the three points positioned atthe substantially equally spaced central angles so that the deflectionof the posture can be reliably suppressed. Because of this small numberof supporting points, moreover, the resistance to the insertion andextraction can be so low that the attachment and detachment of thepreform can be achieved smoothly and reliably.

[0029] In the invention as set forth in claim 5, the means of theinvention as set forth in claim 6 is constructed such that the holderspring is made of a wire-shaped metal member and is generally C-shapedto include three straight portions positioned at the substantiallyequally spaced central angles, and two curved portions connecting theadjoining ones of the straight portions, so that the substantiallycentral portions of the straight portions make external contact with theouter circumference of the peripheral projecting ridge.

[0030] According to the aforementioned construction as set forth inclaim 6, the holder spring has the simple shape which is formed of thegenerally C-shaped metal wire member, so that the three-point supportcan be reliably achieved with the two curved portions and the two endportions abutting elastically against the bottom face of the innercircumference groove and with the three straight portions makingexternal contact with the outer circumference of the peripheralprojecting ridge at their substantially central portions.

[0031] Moreover, the holder spring is enabled by its simple shape tohave easy attachment and detachment and an excellent durability and canbe freed of such a problem that it is brought away from the innercircumference groove by the attachment and detachment of the preform,thereby to achieve a high productivity. By using the simple jig, it ispossible to realize the attachment to and detachment from the innercircumference groove easily while simplifying the maintenance.

[0032] In the invention as set forth in claim 6, the means of theinvention as set forth in claim 7 is constructed such that the metalmember is formed to have such an elliptical section that its flattenedportion makes external contact with the outer circumference of theperipheral projecting ridge.

[0033] According to the aforementioned construction as set forth inclaim 7, the mouth cylinder portion of the preform is inserted with thehelical ridge portion formed on the outer circumference being sliding onthe generally central portions of the straight portions of the holderspring. The sliding face is exemplified by the flattened portion of themetal member having the elliptical section so that the insertingoperation of the preform can be smoothly achieved with the wire-shapedmetal member being not caught by the groove of the helical ridge.

[0034] In the invention as set forth in claim 1, according to the meansof the invention as set forth in claim 8, the support portion isconstructed: by mounting smoothly surfaced ball members in circulartransverse holes, in the state opening onto the inner circumference ofthe cylindrical wall at the leading end portion of said jig body formedto at least three portions at a space of substantially equally centralangles with respect to the center axis of said jig body, such that theball members may be unable to come out and such that they are partiallyprotruded in a pushed state by elastic members; and by providing sealportions in said transverse holes for exhibiting sealing propertiesagainst blow air.

[0035] The aforementioned construction of claim 8 utilizes a functionlike a ball plunger, and the ball members move under pressure in thetransverse holes so that the mouth cylinder portion of the preform canbe smoothly inserted into and extracted from the holding jig by actionssuch as the rotations of the ball members. With the ball members makingexternal contact with the peripheral projecting ridge, moreover, theassembled posture of the preform can be reliably held by the pressure ofthe elastic members. By adjusting the elastic forces of the elasticmembers, still moreover, it is possible to realize the proper insertion,extraction and posture holdability.

[0036] The ball members can be exemplified by those having littledeformation due to an external force but an excellent surfaceslidability, such as stainless steel balls. The elastic members can beexemplified by an O-ring shaped member having elastic or rubberyproperties or by a coil spring.

[0037] Here, the external contacting positions of the aforementionedO-ring, holder spring or balls with the peripheral projecting ridge canbe determined according to the purpose or necessity. It is, however,preferable that the contacting positions are located by abutment againstthe lower end edge of the peripheral projecting ridge. Then, the lowerend edge of the peripheral projecting ridge exhibits the function of theretaining member so that it can support the posture of the preform morereliably.

[0038] In the invention as set forth in claim 1, 2, 3, 4, 5, 6, 7 or 8,the means of the invention as set forth in claim 9 is constructed suchthat a neck ring formed integrally with and circumferentially of thelower end of the outer circumference of the mouth cylinder portion ismade, with the jig body being attached to the blow mold, to make closeabutment against an abutting step portion formed at the leading end openedge portion of the jig body.

[0039] According to the aforementioned construction as set forth inclaim 9, the neck ring makes abutment at its upper face against theabutting step portion to determine the insertion limit of the mouthcylinder portion. Moreover, the neck ring of the preform is clamped,when the preform is mounted in the blow mold, between the blow mold andthe abutting step portion of the jig body so that the preform withrespect to the blow mold is fixed in a predetermined assembled posture.

[0040] Even when the preform is detached from the blow mold, moreover,its neck ring portion is abutting against the abutting step portion sothat the blow molding is held in its posture at the two portions, i.e.,at the peripheral projecting ridge and the neck ring. It is possible toinhibit the rocking motion of the blow molding especially in thetransverse direction.

[0041] By the assembly of the holding jig with the blow mold, moreover,the neck ring of the preform is clamped between the neck supportingflanged portion of the blow mold and the abutting step portion of thejig body. As a result, the neck ring makes close abutment against theabutting step portion so that the sealing against the blow air isachieved.

[0042] Therefore, the neck ring is positioned at the lower end of theouter circumference of the mouth cylinder portion of the preform so thatthe mouth cylinder portion is positioned in its entirety in the blowpressure atmosphere no matter whether its portion might be outside orinside. The blow pressure can act homogeneously on the entire surface ofthe mouth cylinder portion to prevent the occurrence of the defectivedeformation such as the radially enlarged deformation of the mouthcylinder portion.

[0043] In the invention as set forth in claim 1, 2, 3, 4, 5, 6, 7, 8 or9, the means of the invention as set forth in claim 10 is constructedsuch that with the mouth cylinder portion of the preform being insertedto the insertion limit into the leading end portion of the jig bodythereby to hold the posture of the preform, all the constructionportions are spaced by at least one half of the internal diameter of themouth cylinder portion from the center axis of the preform.

[0044] Here, the construction, in which with the posture of the preformbeing held, all the construction portions are spaced by at least onehalf of the internal diameter of the mouth cylinder portion from thecenter axis of the preform, is specified such that the column-shapedspace having the internal diameter of the mouth cylinder portion but noportion to obstruct the flow of air is retained in the region from thepin inserting bore extending through the center of the jig body to theinside of the mouth cylinder portion of the preform.

[0045] According to the aforementioned construction as set forth inclaim 10, the pin inserting bore of the jig body for the passage to feedthe air to the inside of the mouth cylinder portion and the inside ofthe preform is cleared of the portion which obstructs the flow of airinto the preform. The passage of air can be widened to the limit so thatthe flow rate of the blow air can be increased to shorten the blow timeperiod, and the flow rate at the air circulation time can be increasedto improve the cooling efficiency thereby to achieve an improvement inthe productivity.

[0046] Usually, the air blow in the blow molding or the air circulationfor cooling the bottle after blown is executed with the drawing pinbeing inserted in the holding jig and the preform. In the air blow, theblow air flows into the preform mainly from the clearance between theouter circumference of the drawing pin and the inner circumference ofthe mouth cylinder portion. At the air circulation time, the air flowsthrough the passage formed in the drawing pin. According to the purpose,the effective sectional area to be used for the blow air or circulationair to flow can be determined mainly by the external diameter of thedrawing pin.

[0047] In the invention as set forth in claim 1, 2, 3, 4, 5, 6, 7, 8 or9, the means of the invention as set forth in claim 11 is constructedsuch that with a guide cylinder member having a leading end portionradially reduced in a tapered shape and adapted to be inserted into themouth cylinder portion of the preform is so erected into the pininserting bore that its leading end portion is protruded from theleading end of the jig body.

[0048] According to the construction as set forth in claim 11, thepreform can be easily assembled with the holding jig by using theleading end portion of the guide cylinder member radially reduced in thetapered shape, as the guide. It is, therefore, possible to increase thedegree of freedom of the precision design such as the holding jigtransfer apparatus and to reduce the production troubles thereby toimprove the productivity.

[0049] Here, the posture of the preform can be reliably held by theholding jig support portion of the present invention. Therefore, theguide cylinder member for holding the posture need not always bedisposed inside of the preform so that the flow passage of the blow aircan be accordingly widened substantially to the limit, as has beendescribed hereinbefore. In the construction of the present invention,however, it is naturally one of branches for selection to employ thatguide cylinder member in accordance with the mode of using the holdingjig in the manufacture process and the necessity in the manufactureapparatus and the manufacture process.

[0050] In the invention as set forth in claim 1, 2, 3, 4, 5, 6, 7, 8, 9,10 or 11, the means of the invention as set forth in claim 12 isconstructed such that a retained portion to be retained in anunextractable manner in a transfer apparatus is provided in the outercircumference of the root end portion of the jig body.

[0051] According to the aforementioned construction of claim 12, evenwith a resistance by the support portion when the blow molding such asthe blow molded bottle is extracted from the holding jig, the assemblyof the jig body with the transfer apparatus is retained by that retainedportion. Therefore, the jig body is neither raised together with theblow molding nor leaves the transfer apparatus to prevent the troublesin the production line.

[0052] According to the invention as set forth in claim 13, there isprovided means comprising a cylindrical jig body having a pin insertingbore formed therethrough at its center for a drawing pin to be insertedthereinto, and formed into a cylindrical shape having such an internaldiameter that its leading end portion may make loose, external contactwith the mouth cylinder portion of such a preform formed of a syntheticresin into a bottomed cylindrical shape,

[0053] and with the mouth cylinder portion of the preform being insertedto the insertion limit into the leading end portion of the jig bodythereby to hold the preform, all the construction portions are spaced byat least one half of the internal diameter of the mouth cylinder portionfrom the center axis of the preform.

[0054] Here, the construction, in which with the posture of the preformbeing held, all the construction portions are spaced by at least onehalf of the internal diameter of the mouth cylinder portion from thecenter axis of the preform, is specified such that the column-shapedspace having the internal diameter of the mouth cylinder portion but noportion to obstruct the flow of air is retained in the region from thepin inserting bore extending through the center of the jig body to theinside of the mouth cylinder portion of the preform.

[0055] According to the aforementioned construction as set forth inclaim 13, the pin inserting bore of the jig body for the passage to feedthe air to the inside of the mouth cylinder portion and the inside ofthe preform is cleared of the portion which obstructs the flow of airinto the preform. The passage of air can be widened to the limit so thatthe flow rate of the blow air can be increased to shorten the blow timeperiod, and the flow rate at the air circulation time can be increasedto improve the cooling efficiency thereby to achieve an improvement inthe productivity.

[0056] Usually, the air blow in the blow molding or the air circulationfor cooling the bottle after blown is executed with the drawing pinbeing inserted in the holding jig and the preform. In the air blow, theblow air flows into the preform mainly from the clearance between theouter circumference of the drawing pin and the inner circumference ofthe mouth cylinder portion. At the air circulation time, the air flowsthrough the passage formed in the drawing pin. According to the purpose,the effective sectional area to be used for the blow air or circulationair to flow can be determined mainly by the external diameter of thedrawing pin.

[0057] Moreover, the inner circumference of the leading end portion ofthe holding jig makes loose, external contact with the mouth cylinderportion of the preform. When at least the preform is erected upside-downand inserted in the jig body, its posture can be held, and its mouthcylinder portion can be easily inserted into and extracted from theleading end portion of the jig body. According to the purpose, however,the strength of the external contact relating to the holdability of theposture and the insertion and extraction can be adjusted by setting theinternal diameter of the leading end portion of the jig body.

[0058] Here, the insertion limit of the mouth cylinder portion can beset, for example, by the neck ring formed integrally with andcircumferentially of the lower end of the outer circumference of themouth cylinder portion, by the upper end portion of the mouth cylinderportion and the leading end face of the jig body, or the peripheralabutment against the circumferential step portion suitably added.

[0059] In the invention as set forth in claim 13, the means of theinvention as set forth in claim 14 is constructed such that a neck ringformed integrally with and circumferentially of the lower end of theouter circumference of the mouth cylinder portion is made, with the jigbody being attached to the blow mold, to make close abutment against anabutting step portion formed at the leading end open edge portion of thejig body.

[0060] According to the aforementioned construction as set forth inclaim 14, the upper face of the neck ring makes abutment against theabutting step portion to determine the insertion limit of the mouthcylinder portion. While the preform is mounted in the blow mold,moreover, its neck ring is clamped between the blow mold and theabutting step portion of the jig body so that the preform is fixed at apredetermined assembled posture with respect to the blow mold.

[0061] When the preform is detached from the blow mold, on the otherhand, the neck ring portion makes abutment against the abutting stepportion, and the blow molding is held in its posture at the two portionsof the peripheral projecting ridge and the neck ring so that it isreliably inhibited in the rocking motion in the transverse direction.

[0062] By the assembly of the holding jig with the blow mold, moreover,the neck ring of the preform is clamped between the neck supportingflanged portion of the blow mold and the abutting step portion of thejig body so that it makes close abutment against the abutting stepportion thereby to achieve the sealing against the blow air.

[0063] Therefore, the neck ring is positioned at the lower end of theouter circumference of the mouth cylinder portion of the preform so thatthe mouth cylinder portion is positioned in its entirety in the blowpressure atmosphere no matter whether its portion might be outside orinside. The blow pressure can act homogeneously on the entire surface ofthe mouth cylinder portion to prevent the occurrence of the defectivedeformation such as the radially enlarged deformation of the mouthcylinder portion.

[0064] In the invention as set forth in claim 13 or 14, the means of theinvention as set forth in claim 15 is constructed such that a retainedportion to be retained in an unextractable manner in a transferapparatus is provided in the outer circumference of the root end portionof the jig body.

[0065] According to the aforementioned construction of claim 15, evenwith a resistance by the support portion when the blow molding such asthe blow molded bottle is extracted from the holding jig, the assemblyof the jig body with the transfer apparatus is retained by that retainedportion. Therefore, the jig body is neither raised together with theblow molding nor leaves the transfer apparatus to prevent the troublesin the production.

BRIEF DESCRIPTION OF THE DRAWINGS

[0066]FIG. 1 is a front elevation showing the state, in which a firstembodiment of present invention is mounted in a blow mold, with onelefthand half being presented in a longitudinal section.

[0067]FIG. 2 presents a front elevation and a top plan view showing thefirst embodiment of the present invention.

[0068]FIG. 3 is an essential portion enlarged longitudinal sectionshowing the state, in which the first embodiment of the presentinvention is mounted in the blow mold and in which a drawing pin isinserted into the embodiment.

[0069]FIG. 4 is an essential portion enlarged longitudinal section ofthe state, in which a preform is mounted in the first embodiment of thepresent invention.

[0070]FIG. 5 is a top plan view showing an example of a holder spring tobe used in a second embodiment of the present invention.

[0071]FIG. 6 presents a front elevation and a top plan view showing athird embodiment of the present invention.

[0072]FIG. 7 is an essential portion enlarged longitudinal section ofthe state, in which a preform is mounted in the third embodiment of thepresent invention.

[0073]FIG. 8 is an essential portion enlarged longitudinal section ofthe state, in which a preform is mounted in a fourth embodiment of thepresent invention.

[0074]FIG. 9 presents a top plan view (a) and a sectional view (b)showing a C-shaped spring to be used in a fifth embodiment of thepresent invention.

[0075]FIG. 10 presents a front elevation and a top plan view showing thefifth embodiment of the present invention.

[0076]FIG. 11 is a front elevation showing the state, in which a fifthembodiment of present invention is mounted in a blow mold, with onelefthand half being presented in a longitudinal section.

[0077]FIG. 12 is an essential portion enlarged longitudinal section ofthe state, in which a preform is mounted in the fifth embodiment of thepresent invention.

[0078]FIG. 13 is a front elevation showing the state, in which a sixthembodiment of present invention is mounted in a blow mold, with onelefthand half being presented in a longitudinal section.

[0079]FIG. 14 is an essential portion enlarged longitudinal sectionshowing an example of the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

[0080] Embodiments of the present invention will be described in thefollowing with reference to the drawings.

[0081]FIG. 1 shows the state, in which a preform P is attached to aholding jig of a first embodiment according to the present invention andin which the holding jig is mounted in a blow mold 1. FIG. 3 shows thestate, in which a drawing pin 16 is further inserted. FIG. 2 presents afront elevation having half longitudinal section and a top plan viewshowing a jig body 6. The jig body 6 is constructed by merging a fittedcylinder portion 9, which has an external diameter enlarged to be fittedin and assembled with an assembly recess 4 of the blow mold 1, with theupper end of a shank cylinder portion 7, which has such a retainedportion 17 of a circumference groove shape formed in the outercircumference as is to be assembled with the not-shown transferapparatus and which has a relatively smaller external diameter.

[0082] The shank cylinder portion 7 has an internal diameter slightlylarger than that of a mouth cylinder portion P2 of the preform P. Thefitted cylinder portion 9 has such an internal diameter at its lowerportion as is equal to that of the shank cylinder portion 7 and such aninternal diameter over a radially enlarged portion that it can makegentle, external contact with a peripheral projecting ridge P3 toreceive the mouth cylinder portion P2 easily and that it is radiallyenlarged upward in a gently counter-tapered shape. An innercircumference groove 18 a for assembling and holding an O-ring 21 isformed in the inner circumference of the fitted cylinder portion 9 abovethe height position, which confronts the peripheral projecting ridge P3of the mouth cylinder portion P2 when the mouth cylinder portion P2 ofthe preform P is fitted in the fitted cylinder portion 9 from theopening of the upper portion (or the leading end portion) to bring theupper face of a neck ring P1 into abutment against a later-describedabutting step portion 13.

[0083] At the upper end portion of the fitted cylinder portion 9,moreover, there is formed the abutting step portion 13, which makesabutment, while closely contacting, against the upper face of the neckring P1 thereby to determine the fitting limit of the mouth cylinderportion P2 and to exhibit a sealing effect for the blow air. At the blowmolding time, the mouth cylinder portion P2 is positioned in itsentirety in the blow pressure atmosphere and is subjected to the uniformblow pressure all over its surface so that it can be prevented frombeing irregularly deformed or radially enlarged.

[0084] In the present first embodiment, a support portion K isconstructed by assembling and fixing the O-ring 21 with the innercircumference groove 18 a. This O-ring 21 makes external contact withthe lower end edge of the peripheral projecting ridge P3 formedcircumferentially of the mouth cylinder portion P2 of the preform Pthereby to hold the posture of the preform P (as referred to FIG. 1 andFIG. 4).

[0085] Moreover, the neck ring P1 has its upper face abutting againstthe abutting step portion 13 of the fitted cylinder portion 9 (asreferred to FIG. 4), and this abutting portion of the neck ring P1 is inthe state to exhibit the active function to hold the posture of thepreform P. As a result, the preform P has its posture supported at thetwo portions, i.e., the peripheral projecting ridge P3 and the neck ringP1 so that it can be held more reliably in its posture and inhibited inits rocking motion.

[0086] Here, the holding of the assembled position of the preform P withthe holding jig should not be limited to the support by that supportportion K and the abutting step portion 13 for the neck ring P1. In casethe threaded portion of the mouth cylinder portion P2 and the mouthcylinder portion P2 are thermally crystallized (or blushed), forexample, the abutment against the leading end face of the mouth cylinderportion P2 can also act to hold the posture.

[0087] With the jig body 6 is attached to the blow mold 1, moreover, thepreform P is held in its posture by the action of the support portion K,and the neck ring P1 is reliably clamped between the abutting stepportion 13 and a neck supporting flanged portion 3 of the blow mold 1.During the blow-drawing molding operation, therefore, the preform P canalso be reliably inhibited.

[0088]FIG. 3 shows the state, in which the drawing pin 16 is inserted ina pin inserting bore 11 of the jig body 6. The posture of the preform Pcan be reliably held by the support portion K making external contactwith the mouth cylinder portion P2. Unlike the example of the prior art(as referred to FIG. 14), therefore, it is unnecessary to provide aguide cylinder member 10 on the inner side of the preform P for holdingthe posture. Moreover, the shank cylinder portion 7 of the jig body 6has an internal diameter slightly larger than that of the mouth cylinderportion P2 so that no portion to obstruct the flow of air exists.

[0089] Here in the present first embodiment, as in a second, third,fourth or sixth embodiment to be described hereinafter, all thecomponents are spaced, while holding the preform P, at a distance of atleast one half of the internal diameter of the mouth cylinder portion P2from the center axis of the preform P. This construction eliminates theportion, as might otherwise obstruct the flow of air into the preform P,from the inside of the mouth cylinder portion P2 and from the pininserting bore 11 of the jig body 6, which provides the passage forfeeding the air into the preform P. Therefore, the passage of air can bewidened to the limit and retained.

[0090] Here, if the external diameter of the drawing pin 16 is set to asmall value, the clearance to be formed between the outer circumferenceof the drawing pin 16 and the inner circumference of the mouth cylinderportion P2 can be enlarged to increase the flow rate of the blow airaccordingly. By enlarging the diameter of the drawing pin 16, on thecontrary, it is enabled to increase the flow rate of air to becirculated in the drawing pin 16. Thus, the diameter of the drawing pin16 can be selected in conformity with a purpose.

[0091] In case the support portion K of the present embodiment isadopted, on the other hand, a more or less sliding resistance ariseswhen the preform P is extracted upward from the holding jig. However,this extraction can be easily achieved by fixing the jig body 6 on thetransfer apparatus using the retained portion 17 of the circumferencegroove shape formed in the shank cylinder portion 7 of the jig body 6.

[0092] Here in the aforementioned first embodiment, as in the remainingembodiments to be described hereinafter, there is described the case, inwhich the preform P is inserted upside-down into the upright jig body 6and in which this upright posture is held. According to the supportportion K of the present embodiment, however, the posture to be taken bythe preform P should not be limited to the described one but could beheld in any direction according to the purpose or necessity, such as aposture in which the preform P is inserted upward or a posture in whichthe preform P is inserted horizontally. This variable posture has suchan effect in the continuous production process, for example, as to widenthe degree of freedom for designing or arranging the individual units ofthe transfer apparatus or the like.

[0093] In a second embodiment of the holding jig of the presentinvention, the support portion K is constructed by mounting a holderspring 22 in the inner circumference groove 18 a in place of the O-ring21 of the first embodiment. The holder spring 22 exhibits an inwardfastening force with the force of the spring so that it can hold theposture of the preform P more reliably, while making external contactwith the peripheral projecting ridge P3 of the preform P, can beinhibited in its rocking motion.

[0094]FIG. 5(a) shows one example of the holder spring 22, which isrounded in a coiled spring into an O-ring shape. This holder spring 22is fitted in the inner circumference groove 18 a with its innercircumference of the O-ring shape being partially protruded from theinner circumference of the fitted cylinder portion 9, and is brought foruse into abutment against the lower end portion of the peripheralprojecting ridge P3. FIG. 5(b) shows another example of the holderspring.

[0095] The holder spring 22 can select the optimum shape, elastic forceand so on according to the purpose while balancing the inserting andextracting properties of the mouth cylinder portion P2 and the postureholdability, durability and so on of the preform P.

[0096]FIG. 6 presents a front elevation and a top plan view showing thejig body 6 of a third embodiment of the present invention. In the outercircumference of the upper portion of the fitted cylinder portion 9,there is formed an outer circumference groove 18 b for assembling andholding an outer circumference seal ring 26 having properties of rubberelasticity so that ball members 23 may make abutment against the lowerend edge of the peripheral projecting ridge P3 of the mouth cylinderportion P2. From the bottom portion of the outer circumference groove 18b, moreover, there are formed three circular transverse holes 19, whichare so positioned at central angles equally spaced from each other withrespect to the center axis of the fitted cylinder portion 9 as to extendthrough the wall of the fitted cylinder portion 9.

[0097] In the present embodiment, the ball members 23 are made ofstainless steel balls, and the transverse holes 19 are so shaped thattheir inner end portions are slightly radially reduced. When the ballmembers 23 are fitted in those transverse holes 19 and when the outercircumference sealing ring 26 is so set in the outer circumferencegroove 18 b as to hold the ball members 23 from the outside, the ballmembers 23 are partially protruded to the inner circumference of thefitted cylinder portion 9 (as referred to FIG. 7) while being pushed bythe outer circumference seal ring 26.

[0098] Moreover, this outer circumference seal ring 26 constructs a sealportion for exhibiting the sealing properties against the blow pressure,thereby to perform a function to seal the blow air.

[0099] With the mouth cylinder portion P2 being inserted to itsinsertion limit into the fitted cylinder portion 9, the ball members 23are partially retained by the lower end edge of the peripheralprojecting ridge P3, thereby to make it possible to exhibit thefunctions to hold the posture of the preform P and to inhibit therocking motion, more reliably. The attachment and detachment of thepreform P can be executed without any high resistance by the actionssuch as the rotations of the ball members 23 (as referred to FIG. 7).

[0100]FIG. 8 is an explanatory view of another or a fourth embodiment ofthe present invention utilizing the actions of the ball members 23. Aspring 24 performs the function to apply the pressure to the ball member23, and a plug 27 constructions the seal portion to exhibit the sealingproperties against the blow air thereby to perform the function to sealthe blow air.

[0101] Here, the actions by the ball members 23 as in the thirdembodiment and the fourth embodiment can also be achieved by helicallyassembling a commercially available ball plunger having a helical ridgein its outer circumference, with the transverse hole 19 having a helicalridge, in such a state as can hold the seal.

[0102]FIG. 9 to FIG. 12 show a fifth embodiment of the presentinvention, in which a C-shaped spring 31 (as referred to FIG. 9) is usedas the holder spring 22 and in which the guide cylinder member 10 iserected in the pin inserting bore 11 (as referred to FIG. 10).

[0103] In the present fifth embodiment, the shank cylinder portion 7 andthe fitted cylinder portion 9 are made so separate that the guidecylinder member 10 may be added to the jig body 6, and the sealingproperties of the two are retained by a seal portion 37. However, theremaining portions have a structure substantially similar to that of thefirst embodiment. Moreover, the guide cylinder member 10 is erected fromthe upper end portion of the shank cylinder portion 7. However, thisguide cylinder member 10 is radially reduced in a gently tapered shapetoward the leading end portion so that it can be easily inserted intothe mouth cylinder portion P2 of the preform P.

[0104] When the C-shaped spring 31 is set in the inner circumferencegroove 18 a, two curved portions 33 and individually curved two endportions 35 come into elastic abutment against the bottom face 18 a 1 ofthe inner circumference groove 18 a (as referred to FIG. 9(a) and FIG.10). The C-shaped spring 31 is not disengaged by the vibration of theholding jig being moved, for example, so that its posture is stablyheld.

[0105] Moreover, three straight portions 32 slightly protrude at theirgenerally central portions from an inner circumference 18 a 2 of thefitted cylinder portion 9 (as referred to FIG. 9, FIG. 12 and so on).These three points can hold the posture of the preform P to inhibit therocking motion more reliably while making external contact with theouter circumference, especially the lower end edge of the peripheralprojecting ridge P3. Here, this three-point supporting method caninhibit the rocking motion more reliably not only than the two-pointsupport but also the four-point support. As compared with the more-pointsupporting method, moreover, the three-point supporting method isfeatured in that it can achieve the attachment and detachment of thepreform P can be easily achieved.

[0106] Moreover, this C-shaped spring 31 has a remarkably simplestructure and an excellent durability and can be easily replaced byusing a simple jig. The C-shaped spring 31 does not come out due to theaforementioned vibration or the like of the holding jig being moved butcan reduce the trouble in the production so that it can achieve a highproductivity.

[0107] In the present fifth embodiment, moreover, the metal memberforming the C-shaped spring 31 is formed into an elliptical sectionalshape (in which the ratio of the longer diameter to the shorter diameteris set at 2:1 (as referred to FIG. 9(b)). The flattened portion 36 ofthis metal member makes external contact with the lower end edge of theouter circumference of the peripheral projecting ridge P3 (as referredto FIG. 12). When the preform P is to be assembled with the holding jig6, the mouth cylinder portion P2 is inserted with the helical ridgeformed on its outer circumference being sliding on the side face of thegenerally central portion of the straight portion 32 of the C-shapedspring 31. However, the flattened portion 36 of the metal member has thesliding face formed into the elliptical sectional shape so that themetal wire member can achieve the insertion smoothly without beingcaught by the helical groove.

[0108] The posture of the preform P can be reliably held by the holdingjig support portion K of the present invention. It is, therefore, notalways necessary unlike the example (as referred to FIG. 14) of theprior art to provide the guide cylinder member 10 on the inner side ofthe preform P for holding the posture of the same. As has been describedin connection with the first embodiment, however, the flow passage ofthe blow air can be accordingly enlarged substantially to the limit. Inthe construction of the present invention, it is naturally one ofoptions to use the guide cylinder member 10 according to the mode ofusing the holding jig and the necessities in the manufacture process,the manufacture apparatus and so on.

[0109] Here, the present fifth embodiment is constructed by erecting theguide cylinder member 10. By making use of the tapered leading endportion of that guide cylinder member 10, the mouth cylinder portion P2of the preform P can be easily and smoothly assembled with the leadingend portion of the jig body 6. It is possible to relax the precision forpositioning the holding jig transfer apparatus, for example, and toreduce the production troubles more.

[0110] Here, the double blow molding is executed by using the holdingjig of the present fifth embodiment to mold the bottle. A secondaryintermediate molding is not always fixed in its shape due to the thermalshrinkage and it is made slightly smaller in its size than that of thefinal molding. But the secondary intermediate molding can be inhibitedin its rocking motion and held in a predetermined posture, therefore, atthe blow molding step the frequency of occurrence such as the contactwith the bottle or the bite by the split mold could be reduced tosuppress the percent defective to a remarkably low level.

[0111]FIG. 13 shows a sixth embodiment of the present invention, inwhich the support portion K is omitted from the first embodiment but inwhich the leading end portion of the jig body 6 is formed into acylindrical shape having an internal diameter to make loose, externalcontact with the mouth cylinder portion P2. The jig body 6 can hold atleast the posture of the preform P, in which the preform P is invertedand inserted in the jig body 6.

[0112] The fitted cylinder portion 9 has such an internal diameter atits upper portion as can make gentle, external contact with theperipheral projecting ridge P3 to insert the mouth cylinder portion P2easily thereinto and as is radially enlarged upward in a gentlycounter-tapered shape. However, the internal diameter and the taperedshape can be selected considering the balance of the inserting andextracting properties of the mouth cylinder portion P2 into the jig body6 and the holdability of the posture.

[0113] Even in case the support portion K is not adopted as in thepresent embodiment, moreover, with the jig body 6 being attached to theblow mold 1, the neck ring P1 can be reliably clamped between theabutting step portion 13 and the neck supporting flanged portion 3 ofthe blow mold 1 thereby to suppress the rocking motion of the preform Pbeing blown.

[0114] Advantage of the Invention

[0115] The present invention has the construction thus far described sothat it can have the following effects. In the invention as set forth inclaim 1, the assembled postures of the preform and the blow molding canbe reliably held, even when the molding jig is detached from the blowmold, to prevent the occurrence of production troubles, as mightotherwise be caused by losing the posture during the transfer, and thedeflection of the posture of the secondary intermediate being heated inthe double blow molding can be eliminated to prevent the defectivephenomenon such as the bite of the mold.

[0116] Thanks to the construction in which the preform holds itsposition by making external contact with the mouth cylinder portion,moreover, the flow rate of the blow air can be increased to theexcellent moldability and high productivity of a biaxial orientationblow-molded bottle.

[0117] In the invention as set forth in claim 2, the O-ring supports thepreform by making external contact with the entire outer circumferenceof the peripheral projecting ridge of the mouth cylinder portion so thatthe posture of the preform can be held properly and stably by the simplestructure.

[0118] In the invention as set forth in claim 3, the posture of thepreform can be held properly and stably by the elastic force of theholder spring, as set to a desired value.

[0119] In the invention as set forth in claim 4, the mouth cylinderportion is supported at a plurality of points positioned at thesubstantially equally spaced central angles, without making externalcontact with the entire outer circumference of the peripheral projectingridge. Therefore, the attachment and detachment of the preform can beachieved smoothly and reliably with a low resistance to the insertionand extraction.

[0120] In the invention as set forth in claim 5, the mouth cylinderportion is supported at the three points positioned at the substantiallyequally spaced central angles so that the deflection of the posture canbe reliably suppressed. Because of this small number of supportingpoints, moreover, the resistance to the insertion and extraction can beso low that the attachment and detachment of the preform can be achievedsmoothly and reliably.

[0121] In the invention as set forth in claim 6, the holder spring hasthe simple shape which is formed of the generally C-shaped metal wiremember, so that the three-point support can be reliably achieved. Theholder spring can have easy attachment and detachment and an excellentdurability and can be freed of such a problem that it is brought awayfrom the inner circumference groove by the attachment and detachment ofthe preform. A high productivity can be achieved while simplifying themaintenance.

[0122] In the invention as set forth in claim 7, the mouth cylinderportion of the preform is inserted with the helical ridge formed on theouter circumference being sliding on the generally central portions ofthe straight portions of the holder spring. The sliding face isexemplified by the flattened portion of the metal member having theelliptical section so that the inserting operation of the preform can besmoothly achieved with the wire-shaped metal member being not caught bythe groove of the helical ridge.

[0123] In the invention as set forth in claim 8, the ball members canact to hold the posture of the preform stably and to insert and extractthe mouth cylinder portion of the preform smoothly and safely.

[0124] In the invention as set forth in claim 9, the preform can besupported by the neck ring, too, so that the holding of its posture andthe suppression of its rocking motion can be more reliably achieved.

[0125] Moreover, the sealing against the blow air can be achieved by theneck ring so that the blow pressure can act homogeneously on the entiresurface of the mouth cylinder portion to prevent the occurrence of thedefective deformation such as the radially enlarged deformation of themouth cylinder portion.

[0126] In the invention as set forth in claim 10, the holding jig isconstructed by clearing the pin inserting bore of the jig body for thepassage to feed the air to the inside of the mouth cylinder portion andthe inside of the preform, of the portion which obstructs the flow ofair into the preform. With the preform being stably held, the passage ofair can be widened to the limit so that the air flow rate can beincreased to shorten the blow time period and to improve the coolingefficiency at the air circulation time thereby to achieve an improvementin the productivity.

[0127] In the invention as set forth in claim 11, the preform can beeasily assembled with the holding jig by using the leading end portionof the guide cylinder member radially reduced in the tapered shape, asthe guide. It is, therefore, possible to increase the degree of freedomof the precision design such as the positioning of the holding jigtransfer apparatus and to reduce the production troubles thereby toimprove the productivity.

[0128] In the invention as set forth in claim 12, even with a resistanceby the support portion when the blow molded bottle is extracted from theholding jig, the jig body is reliably fixed on the transfer apparatus byusing the retained portion so that it is not raised together to preventthe troubles in the production.

[0129] In the invention as set forth in claim 13, the holding jig isconstructed by clearing the pin inserting bore of the jig body for thepassage to feed the air to the inside of the mouth cylinder portion andthe inside of the preform, of the portion which obstructs the flow ofair into the preform. With the preform being stably held, the passage ofair can be widened to the limit so that the air flow rate can beincreased to shorten the blow time period and to improve the coolingefficiency at the air circulation time thereby to achieve an improvementin the productivity.

[0130] Moreover, the inner circumference of the leading end portion ofthe holding jig makes loose, external contact with the mouth cylinderportion of the preform. When at least the preform is erected upside-downand inserted in the jig body, its posture can be held, and its mouthcylinder portion can be easily inserted into and extracted from theleading end portion of the jig body.

[0131] In the invention as set forth in claim 14, the preform can besupported by the portion of the neck ring, too, so that the holding ofits posture and the suppression of its rocking motion can be morereliably achieved.

[0132] Moreover, the sealing against the blow air can be achieved by theneck ring so that the blow pressure can act homogeneously on the entiresurface of the mouth cylinder portion to prevent the occurrence of thedefective deformation such as the radially enlarged deformation of themouth cylinder portion.

[0133] In the invention as set forth in claim 15, even with a resistancewhen the blow molded bottle is extracted from the holding jig, the jigbody is reliably fixed on the transfer apparatus by using the retainedportion so that it is not raised together to prevent the troubles in theproduction.

1. A preform holding jig for biaxial orientation blow-molding mounting asupport portion (K) holding an assembled posture of a preform (P) havinga bottomed cylindrical shape formed by a synthetic resin which isassembled by inserting a mouth cylinder portion (P2), until an insertionlimit, into the leading end portion of a cylindrical jig body (6) inwhich a pin inserting bore (11) is formed in the center for inserting adrawing pin (16) therein. Wherein said support portion (K) is disposedin the inner circumference of the leading end portion of said jig body(6) at a position opposed to a peripheral projecting ridge (P3) of saidmouth cylinder portion (P2), and for making external contact with theouter circumference of said peripheral projecting ridge (P3) as to becapable of inserting and extracting said mouth cylinder portion (P2). 2.A preform holding jig for biaxial orientation blow-molding, as set forthin claim 1, wherein an O-ring (21) is assembled and fixed in an innercircumference groove (18 a) formed in the inner circumference of theleading end portion of said jig body (6), thereby to construct saidsupport portion (K).
 3. A preform holding jig for biaxial orientationblow-molding, as set forth in claim 1, wherein a holder spring (22) isassembled and fixed in an inner circumference groove (18 a) formed inthe inner circumference of the leading end portion of said jig body (6),thereby to construct said support portion (K).
 4. A preform holding jigfor biaxial orientation blow-molding, as set forth in claim 3, whereinthe holder spring (22) makes external contact with the outercircumference of the peripheral projecting ridge (P3) of the preform (P)at a plurality of points positioned at substantially equally spacedcentral angles.
 5. A preform holding jig for biaxial orientationblow-molding, as set forth in claim 4, wherein the holder spring (22)makes external contact with the outer circumference of the peripheralprojecting ridge (P3) of the preform (P) at three points positioned atsubstantially equally spaced central angles.
 6. A preform holding jigfor biaxial orientation blow-molding, as set forth in claim 5, whereinthe holder spring (22) is made of a wire-shaped metal member and isgenerally C-shaped to include three straight portions (32) positioned atthe substantially equally spaced central angles, and two curved portions(33) connecting the adjoining ones of said straight portions (32), sothat the substantially central portions of said straight portions (32)make external contact with the outer circumference of said peripheralprojecting ridge (P3).
 7. A preform holding jig for biaxial orientationblow-molding, as set forth in claim 6, wherein the metal member isformed to have such an elliptical section that its flattened portion(36) makes external contact with the outer circumference of theperipheral projecting ridge (P3).
 8. A preform holding jig for biaxialorientation blow-molding, as set forth in claim 1, wherein said supportportion (K) is constructed: by mounting smoothly surfaced ball members(23) in circular transverse holes (19) formed in at least three portionsat substantially equally spaced central angles with respect to thecenter axis of said jig body (6), such that they may be unable to comeout and such that they are partially protruded in a pushed state byelastic members; and by providing seal portions in said transverse holes(19) for exhibiting sealing properties against blow air.
 9. A preformholding jig for biaxial orientation blow-molding, as set forth in claim1, 2, 3, 4, 5, 6, 7 or 8, wherein a neck ring (P1) formed integrallywith and circumferentially of the lower end of the outer circumferenceof the mouth cylinder portion (P2) is made, with the jig body (6) beingattached to the blow mold (1), to make close abutment against anabutting step portion (13) formed at the leading end open edge portionof said jig body (6).
 10. A preform holding jig for biaxial orientationblow-molding, as set forth in claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, whereinwith the mouth cylinder portion (P2) of the preform (P) being insertedto the insertion limit into the leading end portion of the jig body (6)thereby to hold the posture of said preform (P), all the constructionportions are spaced by at least one half of the internal diameter ofsaid mouth cylinder portion (P2) from the center axis of said preform(P).
 11. A preform holding jig for biaxial orientation blow-molding, asset forth in claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, wherein with a guidecylinder member (10) having a leading end portion radially reduced in atapered shape and adapted to be inserted into the mouth cylinder portion(P2) of the preform (P) is so erected into the pin inserting bore (11)that its leading end portion is protruded from the leading end of thejig body (6).
 12. A preform holding jig for biaxial orientationblow-molding, as set forth in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11,wherein a retained portion (17) to be retained in an unextractablemanner in a transfer apparatus is provided in the outer circumference ofthe root end portion of the jig body (6).
 13. A preform holding jig forbiaxial orientation blow-molding, comprising a cylindrical jig body (6)having a pin inserting bore (11) formed therethrough at its center for adrawing pin (16) to be inserted thereinto, and formed into a cylindricalshape having such an internal diameter that its leading end portion maymake loose, external contact with the mouth cylinder portion (P2) ofsuch a preform (P) formed of a synthetic resin into a bottomedcylindrical shape, wherein with the mouth cylinder portion (P2) of saidpreform (P) being inserted to the insertion limit into the leading endportion. of said jig body (6) thereby to hold said preform (P), all theconstruction portions are spaced by at least one half of the internaldiameter of said mouth cylinder portion (P2) from the center axis ofsaid preform (P).
 14. A preform holding jig for biaxial orientationblow-molding, as set forth in claim 13, wherein a neck ring (P1) formedintegrally with and circumferentially of the lower end of the outercircumference of the mouth cylinder portion (P2) is made, with the jigbody (6) being attached to the blow mold (1), to make close abutmentagainst an abutting step portion (13) formed at the leading end openedge portion of said jig body (6).
 15. A preform holding jig for biaxialorientation blow-molding, as set forth in claim 13 or 14, wherein aretained portion (17) to be retained in an unextractable manner in atransfer apparatus is provided in the outer circumference of the rootend portion of the jig body (6).